<template>
   <div>
     <h2>计数器</h2>
     <h3>{{$store.state.b.num}}</h3>
     <button @click="increment">+</button>
   </div>
</template>

<script>
export default {
  methods:{
    increment(){
      this.$store.commit('b/increment_Sync')
    }
  }
}
</script>

<style>

</style>